The present invention relates to a computerized system for measuring and storing test data for certain pulmonary functions. The system includes a programmable digital computer for analyzing the stored test data and comparing it with standardized predicted values. The test measurements and related predicted values are then printed on a permanent record.
The present system uses a spirometer to generate an electrical signal representative of the volume of air expired or inspired by a person under test who is undergoing a breathing maneuver under instructions of an operator. One such spirometer is disclosed in the Jones U.S. Pat. No. 3,771,512, issued Nov. 13, 1973 for "System for Measuring Timed Forced Expiratory Volume". This spirometer also includes a chart recorder for making a permanent record of the breathing exercise.
In the present system, the analog signal representative of expired breath is fed to a digital computer. The computer controls a matrix printer, and the system also includes a keyboard for the entry of identification data into the system and for enabling the operator to control the system to measure and record the test data for the various tests.
The computer contains a stored program for communicating, through the printer, to the operator what, if anything the operator should be doing. The computer also stores predicted value for each of the various tests, depending upon the age, sex and height of the test subject.
In operation, when the system is first energized, the computer actuates the printer to print the phrase "ENTER ID DATA" which tells the operator to enter identification data for the subject by means of the keyboard. The exact contents of this data will be discussed more fully within. After the identification data is entered, the computer actuates the printer to print the phrase "SELECT OPTION". This tells the operator that he should communicate back to the computer which test is going to be run. The operator or clinician may then take as much time as is required to instruct the test subject regarding the specific breathing maneuver that is required for the selected test. Although others may be added, the present system is designed to accommodate four separate tests: Forced Expiratory Volume (FEV) Test, a Maximal Voluntary Ventilation (MVV) Test, a Minute Ventilation (MV) Test, and a Functional Residual Capacity (FRC) Test. Depending upon which test is desired to be run, the operator then presses a key on the keyboard representative of the selected test. For example, if it is desired to execute the Forced Expiratory Volume Test, then the key labelled "FEV" is depressed by the operator. The computer receives the information and causes the printer to print FEV thereby verifying to the operator which test has been selected and indicating to the operator that he may then proceed with the actual test procedure.
The test subject then executes the breathing maneuver into the spirometer. An analog signal representative of the expired volume is fed to the computer, and the computer samples this analog signal at a predetermined rate and stores the digitalized samples internally until the test is completed.
The computer then analyzes the acquired data in a preliminary fashion and determines whether the test is a valid test. If not, it will notify the operator by printing the phrase "CANCEL". If the computer determines that the storage test data represents a valid test, it prints the phrase SELECT OPTION. At this time, if the operator, upon inspection of the recorded graph, determines that the test data is in fact valid, he may then cause a printout by means of the keyboard, or if the test data is not valid, he may re-select the test, or select and execute a separate test, such as Maximal Voluntary Ventilation.
After the test data has been acquired and stored, and the operator has determined that a test is valid, if the operator causes a print-out, the computer will analyze the test data, compare it with internally stored data representative of standardized predicted values and print out the subject's identification data, followed by the predicted value, measured value and percentage deviation for each test parameter for that particular test.
The computing hardware incorporated in the present invention employs a microminiaturized computer, and circuitry is included for entry of test data into the computer and recall of that data for analysis after entry. The entire computing system, including the printer may be housed in a module about the size of a portable typewriter. Hence, the computer may be easily transported, rendering the system suitable for mass testing in the field--for example in industrial plants.
Further, the specific hardware using certain available components and including other designed connections and circuits renders the system economical. That is, the cost of the entire computing system is about 10-20 percent of the cost that would be required for a general purpose programmable computer adapted to perform similar functions and having similar computational capacity.
One of the major operational features of the present invention is that it eliminates many sources of error that would otherwise be present or possible in a pulmonary analyzer.
In the present system, the analog signal from the spirometer is fed directly to the computer, thereby eliminating possible human error that would otherwise occur in the transfer of data, for example, from a chart or a meter to a permanent record. Hence, one of the features of the present invention is a direct coupling of the measurement signal to the computer which digitalizes it and stores it immediately. It is this stored information which is later used for analysis purposes.
Further, since the computer is programmed to accept only certain sequences during various test maneuvers, it is able to analyze the measurement data according to established criteria to determine whether the test measurement data is valid, and if it is not, to give an indication to an operator through the printer.
Thus, the present invention insures the proper sequence of operations in conducting a test and obtaining test data. It further obviates the need for some of the judgments made by an operator or technician in assessing the validity of a specific test by establishing predetermined criteria which are stored in the computer.
The present invention eliminates another common source of error which occurs in comparing the observed data with prediction tables and prediction computations. The present invention makes comparisons and computations to arrive at predicted normal values, and the deviations of observed data from the predicted normal values in the computer. Further, the computer is capable of being re-programmed to immediately compare prior "baseline" tests.
Still another common source of error which is obviated by the present invention is the transferring of test results to a permanent record. The present system provides an automatic print-out of the subjects identification, test measurements and comparison with predicted normal values on a single compact record--namely, a paper tape which serves as a permanent record, and one which is capable of being photocopied, for example, for transferring test data to a referring physician.
By providing printed test data in digital form, the present system enables an operator to more readily assess whether the characteristics of a particular test indicate that it is valid in light of his experience.
Because the present system is programmable, it can be re-programmed to update data as technology advances, or to include additional tests or test parameters or new predicted normal values, as they become available or are considered more important than what is presently being done. The system can also be modified to process other supplementary test data such as audiometry, cardiac stress testing, etc., which data may be useful in multi-phase testing programs.
Another feature of the invention is the dot matrix printer which is capable of printing the data in different characters, such as Russian, Hebrew, Arabic, etc. at an extremely high speed in comparison with conventional teletype machines.
Still further, the present invention provides data for tests, and displays that data, which has not previously been displayed. For example, mid-expiratory flow rate (FEF 25-75 percent) is considered to be an important indication of sensitivity, and the present invention computes and displays this parameter. Additional capabilities may be added by computing closing volumes, and flow volume loop parameters, among others.
It will thus be appreciated that the present system is an economical, yet extremely reliable and accurate system for analyzing various pulmonary functions. Other features and advantages will be appreciated by persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing.